Does anyone have have an experience with wrong gender prediction??

I had an elective ultrasound to predict gender when I was 14 weeks. They were very confident my baby is a boy. But now my mom has me freaking out because she says that she read that gender predictions can be wrong a lot of times if it is done before 20 weeks. It looks like a penis to me. I also have an anatomy scan in 3 weeks where the doctor will tell me the gender. Has anyone had an experience where they were told one thing and then told something else at another time? Thank you for all your input.